<!DOCTYPE html>
<html lang="zh">
	<head>
	<style type="text/css">
	div {
		position:absolute;
		top:50%;
		left:50%;
		margin:-150px 0 0 -200px;
		width:400px;
		height:300px;
		border:1px solid red;
	}
	</style>
	</head>
	<body>
		<div>
			<h1>404啦</h1>
		</div>
	</body>
</html>